The present invention relates to a door lock apparatus of an electric cooker and, more particularly, to a door lock apparatus for locking a door in a closed position.
An electric cooker such as a microwave oven has been widely used. The microwave oven supplies microwave energy generated by a magnetron to a heating chamber so as to heat food to be cooked. In a composite type microwave oven, however an electric heater is further disposed in the heating chamber. Each of these electric cookers is provided with a door lock apparatus for locking a door in a closed position to effectively cook foods and to avoid break out microwave energy from the heating chamber. The door lock apparatus has a hook and a handle. The hook pivotally mounted on the door can engage with the housing to lock the door in the closed position and thus securely close the opening. The handle is pivotally mounted on the front outer surface of the door. A rod-like pusher is disposed in the door between the hook and the handle. The pusher is supported by a pusher guide mounted on the door so as to be movable in a straight line along the axial direction thereof. The handle has a pressing surface which abuts against one end of the pusher. The hook has a pressing surface which abuts against the other end of the pusher. When the handle is pivoted, the pusher is urged by the pressing surface of the handle and moves straight toward the hook. The pusher then urges the pressing surface of the hook. As a result, the hook is pivoted to mechanically disengage from the housing, and the door can be opened.
The microwave oven has a switch for controlling oscillation of the magnetron. The switch is operated in accordance with the opening/closing of the door. In other words, the switch is actuated in response to pivotal movement of the hook. The magnetron can be oscillated only when the door is closed.
The pressing surface of the handle is conventionally flat, so that upon pivotal movement of the handle, the urging force acts on the pusher in a direction perpendicular to the pressing surface of the handle. At the beginning of pivotal movement of the handle, the direction of the urging force acting on the pusher through the pressing surface is substantially the same as the axial direction of the pusher. Therefore, the pusher is smoothly displaced. However, the handle exerts force on the pusher in a direction inclined to the axis of the pusher while it is being pivoted. For this reason, the pusher is pressed onto the inner surface of the pusher guide. Frictional force between the pusher and the pusher guide is thus increased, so that a large force is required to pivot the handle. In addition to this disadvantage, the pusher and the pusher guide tend to wear away and deform. The pivotal movement of the handle, and hence the opening/closing operation of the door, becomes unstable. The press surface of the hook is also flat, and so the above problem also arises in the relationship between the pusher and the pressing surface of the hook. When the pusher and the pusher guide become worn away and deformed, the pusher cannot properly pivot the hook. Therefore, the operation of the switch becomes unstable, and microwave energy may leak out.